Mash-up is a word that one hears frequently these days. Definitions of the word are still evolving - there are data mash-ups, consumer mash-ups and business mash-ups. that are beginning to be understood by a small population of developers and vendors.
I think that we are at the beginning of the evolution of the word mash-up, and what it means. Basically, mash-up is a mixture. One can mix data from different sources - as done in data mash-ups, one can present in novel intriguing ways - as done in consumer mash-ups, and one can present it in unique way to bring out some aspect of the data which is now visually easier to recognize - as done in business mash-ups. But those are only the early mash-ups, the first-borns, if one may say so, of a species that will soon thrive and multiply.
One mash-up, that I think is just on the horizon, is the mashup of user experience. A mash-up that will enable users to experience information where they want it, regardless of where they are at this time. Whether on their desktop, or on a web site.
Experience web news when on Word. Or experience a Excel table, when viewing stock news on a financial news and stock movements. Mash-up information interfaces and tools and enable a seamless user experience of information where they want it, without worrying about which interface tool they should pick up. Not just about data, but about user experience. A mash-up that merges our private desktop world, with the outside web world, and in a manner that puts us in control.